Electrical circuit for discharge tubes



June 15, 1954 J, 5. LONG ,68

ELECTRICAL CIRCUIT FOR DISCHARGE TUBES Filed March 20, 1951 /.f f k) zfi ,7 /6 /6 INVENTOR Jhw 5 LONG- ATTORNEYG Patented June 15, 1954 UNITEDSTATES PATENT OFFKIE John E. Long, Midland, Tex.

Application March 20, 1951, Serial No. 216,524

- 7 Claims. 1

This invention relates to a fluorescent lamp lighting system adapted tobe operated either on direct or alternating current.

An object of this invention is to provide a fluorescent lamp arrangementthat may be energized either from a direct current supply or from analternating current supply.

Another object of this invention is to provide a fluorescent lamparrangement in which a current limiting device is automaticallyconnected into the lamp circuit when the lamp is energized from a directcurrent source.

Another object of this invention is to provide a fluorescent lampadapted to be operated either from direct current or alternating currentsupply sources, the lamp circuit having a series connected currentlimiting resistor and a relay for controlling the connection of thiscurrent limiting resistor.

Still another object of this invention is to provide a fluorescent lamparrangement that enables the use of the fluorescent lamp either onalternating or direct current automatically. This arrangement employs acurrent limiting resistor that is short circuited when the lamp isconnected to an alternating current source and to which the shortcircuit is automatically connected when the lamp is connected to adirect current source.

Other and further objects of this invention will be apparent to thoseskilled in the art to which it relates from the following specification,claims and drawing.

In accordance with this invention there is provided an improved circuitfor fluorescent lights which permits the use of these lights either onalternating or direct current automatically. This arrangement employs aconventional inductive type ballast that is connected in series with thefluorescent lamp and in addition to this inductive ballast there isprovided a current limiting resistor for use in series with the lampwhen the lamp is connected to a direct current source. A relay isemployed for controlling a connection across this current limitingresistor and this relay is adapted to be energized selec- 1 tivelyeither by alternating or direct current. In the form of this inventionin which the contacts of the relay that are connected to short circuitthe current limiting resistor, are normally open, the relay is connectedin series with a capacitor so as to be energized only by alternatingcurrent. Thus the contacts of the relay are closed to short circuit thecurrent limiting resistor when the'relay is energized by alternatingcurrent.

found convenient.

In a modified form of this invention the relay is connected in serieswith a choke coil having a high reactance with respect to the relay coilat the power supply frequency and this choke coil prevents sufficientcurrent from flowing to actuate the relay coil when the lamp isconnected to an alternating current supply. The relay coil however, issufficiently energized when direct current is employed and the circuitwhich short circuits the current limiting resistor is thus opened sothat the current limiting resistor is connected in series with the lampwhen a direct current source is employed.

Further details of this invention will be set forth in the followingspecification, claims and drawing.

Referring to the drawing briefly:

Figure 1 illustrates the circuit arrangement of one embodiment of thisinvention; and

Figure 2 illustrates the circuit arrangement of a modified form of thisinvention.

Referring to the drawing in detail, there is illustrated a lamp it whichconsists of a tubular glass envelope having a pair of filaments H and 12that are adapted to be heated to electron emissive temperatures. Thesefilaments are disposed one at each end of the tubular envelope and theyare connected to terminals 13-44 and l5l6 respectively, which areadapted to be connected to suitable sockets such as are well known inthe art.

While the lamp i ll is illustrated as an elongated and straight tube, itis, of course, understood that it may take various shapes such as may beIn general, the inside surface of the glass tube is provided with acoating of fluorescent material which is caused to fluoresce upon beingbombarded by light produced through the ionization of a very smallquantity of mercury or other substance placed inside of the lamp. Whilethis invention is especially adapted to conventional fluorescent lamps,it may also be used in connection with ultra violet lamps that do nothave a coating of fluorescent material on the inside thereof but areemployed primarily as sources of ultra violet light.

The filament terminals l4 and I8 are connected to opposite sides of thestarting switch I! which may be either a manually operated or athermally operated switch. The terminal 13 is connected to one side ofthe relay coil I8 and to one side of the A. C. or D. C. current supplysource which may be the conventional 115 volt lighting current supply.The terminal i5 is connected to one side of the current limitingresistor 3 I9 and to one of the relay contacts 28. The other side ofthis resistor 99 is connected to the other relay contact 2| and to oneside of the ballast impedance 22. The other side of this impedance 22 isconnected to the upper terminal of the capacitor and through the switch24 to the other terminal of the 115 volt lighting circuit. The lowerterminal of the capacitor 23 is con nected to the upper terminal of therelay coil It.

The contacts as and 2| of the relay shown in Figure l are normally openwhen the lamp circuit is deenergized or when it is energized by directcurrent. Therefore, when the switches H and 24 are closed so that thecircuit of the lamp is completed to the source of current supply, thecurrent limiting resistor I9 will be connected in series with the lampif the current supply consists of a direct current source. However, ifthe current supply is an alternating current source then an alternatingcurrent will flow through the winding 68 of the relay and the magneticfiel of this winding will pull down the armature car-- rying the contact2! so that this contact engages the contact 22!] and short circuits theresistor 19. The relay winding 83 is not energized when direct currentis supplied to the lamp because the capacitor 23 blocks passage ofdirect current through the relay winding 18.

When the lamp is connected to the source of current supply as mentionedabove, the filaments H and 42 are heated and produce a conductive vaporinside of the lamp. The circuit of the starting switch H is theninterrupted. How ever, the voltage between the filaments l i and i2causes current to flow through the conductive atmosphere oi the lamp.The radiation or glow produced by this current flow may be to producefluorescence in the flow coating on the inside of the lamp or it may beused as a source of ultra violet light.

When alternating current is employed for energizing the lamp, theresistor I9 is short circuited and the inductive impedance 22 functionsto limit the current flow through the lamp. However, when direct currentis employed for energizing the lamp the direct current resistance of thewinding 22 is insufficient to limit the current flow through the lampand therefore the current limiting resistor 59 is employed in additionto the winding 22 to prevent the current through the lamp from becomingexcessive.

In Figure 2 there is shown a modified form of this invention andcorresponding parts of Figure 2 are designated by the same referencenumerals as in Figure l. In Figure 2 however, the contacts a and Zia ofthe relay are normally closed when the circuit is deenergized or when itis energized by alternating current. However, when the lamp circuit isenergized by direct current the relay winding Ilia is also energizedthrough the choke coil 25 and the current limiting resistor 26 which areconnected in series therewith and the relay armature carrying thecontact 2 in: is pulled down so that the circuit between the contacts213a and 2 la is open. Thus the current limiting resistor i9 is insertedinto the lamp circuit when the lamp is energized from a direct currentsource. This resistor l9 however, re mains short circuited when the lampis energized from an alternating current source because the impedance ofthe circuit of the relay winding, Ida, the resistor 26 and choke coil 25is high enough to limit the current through the winding I80: to a lowvalue insufiicient to operate the relay and the contacts 20a and 21atherefore 4 remain closed and short circuit the resistor l9.

While I have described and illustrated the preferred embodiments of thisinvention in detail in the foregoing specification and the drawing, itis not desired to limit this invention to the exact detail described andshown except insofar as they may be defined by the claims.

What I claim is:

1. An electric lighting system adapted to be operated either on directcurrent or alternating current, the combination of a gas discharge typelamp having a pair of filamentary electrodes, a ballast impedanceincluding an auxiliary resistor portion, primary conductors connectingsaid ballast impedance and electrodes in series across a source ofcurrent supply, a relay, cross conductors connecting said relay to saidsource of current supply across said conductors, anterior to saidballast impedance, switch means actuatable by said relay across saidresistance portion of said ballast impedance, controlling the shortcircuiting or the latter and selective current blocking means permittingthe passage or" only one of said currents, interposed in series withsaid cross conductors, operable under conditions set up on circuitexcitation by said one current but not by the other, to energize saidrelay, whereby the en izing of the winding of said relay from eitheralternating current or direct current is selectively controlled.

2. An electric lighting adapted to be operated either on direct currentor alternating current, the combination or a gas discharge type lamphaving a pair of filamentary electrodes, a ballast impedance includingan auxiliary resistor portion, primary conductors connecting saidballast impedance and electrodes in series across a source of currentsupply, a relay, cross conductors connecting said relay to said sourceof current supply across said primary conductors, anterior to saidballast impedance, switch means operable by said relay across saidresistor portion, controlling the short circuiting of the latter whenthe electrodes are energized by alternating current and means interposedin said cross conductors, preventing the energizing oi the winding ofsaid relay when said source of current supply consists of a directcurrent source.

3. In an electric lighting system adapted to be operated either ondirect current or alternating current the combination of a gas dischargetype lamp having a pair of filamentary electrodes, a choke coil, aresistor, connections connecting said choke coil and said resistor andsaid electrodes in series across a source of current supply, a relayhaving contacts short circuiting said resistor when said lamp isenergized by alternating current, and means connecting the winding ofsaid relay to said source of current supply and controlling saidcontacts when said winding is energized.

4. In an electric lighting system adapted to be operated either ondirect current or alternating current the combination of a gas dischargetype lamp having a pair of filamentary electrodes, a choke coil, aresistor, connections connecting said choke coil and said resistor andsaid electrodes in series across a source of current supply, a relayhaving contacts short circuiting said resistor when said lamp isenergized by alternating current, and means including an impedanceconnecting said relay to said source of current supply and controllingsaid contacts when said relay is energized.

5. In an electric lighting system adapted to'be operated either ondirect current or alternating current the combination of a gas dischargetype lamp having a pair of filamentary electrodes, a choke coil, aresistor, connections connecting said choke coil and said resistor andsaid filaments in series across a source of current supply, a relayhaving contacts short circuiting said resistor when said fluorescentlamp is energized by alternating current, and connections connectingsaid relay across said source of current supply, said last mentionedconnections having means preventing the energizing of the winding ofsaid relay when said source of current supply consists of a directcurrent source.

6. In an electric lighting system adapted to be operated either ondirect current or alternating current the combination of a gas dischargetype lamp having a pair of filamentary electrodes, a choke coil, aresistor, connections connecting said choke coil and said resistor andsaid electrodes in series across a source of current supply, a relayshort circuiting said resistor when said lamp is energized byalternating current, and connections connecting said relay across saidsource of current supply, said last mentioned connections including acapacitor preventing the energizing of the Winding of said relay whensaid source of current supply consists of a direct current source.

'7. In an electric lighting system adapted to be operated either ondirect current or alternating current the combination of a gas dischargetype lamp having a pair of filamentary electrodes, a choke coil, aresistor, connections connecting said choke coil and said resistor andsaid electrodes in series across a source of current supply, a relayshort circuiting said resistor when said lamp is energized byalternating current, and connections connecting said relay across saidsource of current supply, said last mentioned connections including achoke coil preventing the operation of said relay when said source ofcurrent supply consists of an alternating curent source.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,873,402 Lecorguillier Apr. 10, 1945 2,456,870 Francis Dec.21, 1948 FOREIGN PATENTS Number Country Date 25,814 Australia Dec. 24,1935 of 1935

